The present invention provides a gas generator for a restraining device for a vehicle, including: an igniter attached via an igniter collar to an opening in a housing bottom portion; the igniter collar including a main body portion that supports the igniter and an attachment portion that is fixed to the housing bottom portion; at least part of the attachment portion absorbing strains caused by deformation of the housing, sealing between the housing and the igniter collar, by deforming itself correspondingly to deformation of the housing when the housing deforms during the actuation.